Early Google employee and YouTube leader Susan Wojcicki has a simple thought when it comes to competition with Facebook: they're doing their thing and we're doing ours.

That said, she wasn't afraid to diss her competitor just a wee little bit while on stage at the Fortune Brainstorm Tech conference in Aspen, Colorado, on Monday.

First of all, she wanted to make it clear that everyone jumping into online video is staring at a "huge market, any way you look at it."

Americans spend over 4 hours a day watching TV (a stat that amazes Wojcicki, she said). The TV advertising business is about a $150 billion market and the subscription business is $250 billion, she said.

And that's changing as the younger generation stops watching TV the old fashioned way, preferring internet streaming over live TV.

So the fact that Facebook and Twitter "see this is a big opportunity and are coming into market" is "not a surprise," she says.

"Facebook views are different," she says. "They come in a feed on autoplay."

YouTube's 1 billion users are deliberately clicking to watch videos. "We want users to be engaged," she said. And with the 'watch time' metric "we know users continued to watch it."

Plus, she insists, despite how huge YouTube is already, "We see it accelerating. We have over 1 billion users globally, 'watching time' year-over-year is growing at over 50%."

That said, instead of focusing on how to beat Facebook's video business, she's focused on YouTube's list of priorities.

Her top three priorities are "Mobile, mobile, mobile," she says. "The majority of our views are on mobile. We want to make the user interface better, creation experience better, make it faster. Mobile is changing everything and it will change it more in future," Wojcicki says.